Mukotsu from Inuyasha is very small and toad-like compared to normal humans, and he's shown melting and suffocating people with his poisons. He also tries to do something nasty to a helpless Kagome, before being bifurcated by Sesshomaru.

Mini-me from Austin Powers is a lighter example. He's not that depraved, but he does try to eat a live cat at one point.

Considering the stock he is cut from, the dwarfism is probably not the main cause.

Subverted in Foul Play; "The Dwarf" that Gloria is warned about isn't really a dwarf. This, of course, leads to confusion, and when she meets an actual dwarf, she goes nuts and throws him out of her apartment, seriously injuring him, only to find out he's really a bible salesman.

Death at a Funeral has the dwarf who blackmails the family with compromising pictures of him and the family patriach engaged in questionable acts.

Olaf, the title character of the Danish Exploitation FilmThe Sinful Dwarf, lures young women into an attic and locks them up. They are later used for prostitution. Yes, the word "depraved" might be a little light in this case.

Harry Earles plays what might be the Ur Example in The Unholy Three. He is easily the most vicious and evil of the titular trio, and pulls off the old 'midget in a baby carriage' trick.

Downplayed with Nick Nack of The Man with the Golden Gun. He's Affably Evil at all times, but he does work for a renowned contract killer, and does not hesitate to try and kill others when he feels like it.

In the book Obsidian Butterfly, part of the Anita Blake Vampire Hunter series, there is Nicky Bako, a pretty infamous necromancer who is the witch for the outlaw biker gang and werewolf pack in the area, Los Lobos.

This is what everyone thinks Tyrion is, despite his being one of the only characters that's basically good. But he may have had a Start of Darkness because of his ill treatment.